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The present invention relates to endoscopy, and in particular to an endoscopy illumination system wherein (i) illumination is based on (stroboscopic) light pulses using at least one light-emitting element (e.g., a light emitting diodexe2x80x94LED) to obtain illumination of intracorporal structures, including the vocal folds, and where (ii) the light-emitting elements are powered and controlled by an electronic control unit within the endoscopy illumination system comprising features to obtain stroboscopic imaging.
In order to provide background information so that the invention may be completely understood and appreciated in its proper context, a short paragraph is given to acknowledge important inventions in the history of endoscopy of the larynx, and particularly stroboscopy, and reference is made to a number of prior art publications and patents.
Historically, the visualization of the inner parts of the body is referred to as endoscopy. Laryngoscopy specifically refers to the visualization of the larynx, which contains the sound producing vocal folds (also called vocal cords). Visualization of the larynx was first described by Garcia in the middle of the 19th century when he used a mirror placed in the pharynx to observe vocal fold motion. For the past hundred years, the use of mirrors has been considered routine for laryngologists. The rapid vibrations of the vocal folds cannot be detected using continuously emitting light sources, because typical frequencies for voice production ranging from 70 Hz up to 400 Hz are too fast for our eyes to see. The technique of stroboscopy allows the physician a clear view of the vocal folds, even when they are vibrating rapidly. In 1878, Oertel used a device to visualize the rapid vocal fold motions during sound production (phonation) through the use of stroboscopy techniques. Since then, three major image routing techniques werexe2x80x94and currently still arexe2x80x94used clinically to help visualize the vocal fold motions via stroboscopy: (a) indirect observation with a mirror held into the pharynx of the examinee and illumination provided by an external light source, (b) intrapharyngeal placement of a rigid endoscope (also called a telescope) through the mouth (transorally), whereby the telescope contains an optical apparatus with lenses and mirrors as well as light conductors for illumination of the pharynx and larynx, and (c) the use of a fiberscope, with its far end also placed within the pharynx, but routed through the nasal cavity (transnasally), wereby the fiberscope contains an optical compartment for image transmission as well as glass fiber light conductors for illumination. In all three techniques, illuminating light is provided through extracorporal light sources.
For non-moving anatomical structures, color images are preferred clinically because they contain more information than monochrome images. For the examination of dynamic features, e.g., the vibration patterns of the vocal folds using stroboscopy, monochrome images with high gray scale resolution are considered sufficient. Numerous publications considering dynamic behavior of the vibrating vocal folds are based on black and white imaging. A historical overview of stroboscopy from the perspective of a clinician is given in an article by J. Wendler (Stroboscopy. Journal of Voice, Vol.6 No.2, pp 149-154, 1992, Raven Press, N.Y.). Although the technique of stroboscopy has been known and used for more than a hundred years, stroboscopy systems still are heavy, large, and expensive to build.
Because LEDs are used for illumiination in the preferred embodiment of this invention, some features may be pointed out in advance. Energy supplying elements, such as batteries, are capable of powering an electronic circuit as well as an illumination source, e.g. LEDs. LEDs are also a quite cheap light source (a red LED with very bright light emission presently costs about 0.80 US$). Light intensity is mainly dependent on current flow, and usually an upper current thresholdxe2x80x94for continous light emission purposesxe2x80x94is typically at 20 Milliamperes (mA). More precisely, a continuous current of 20 mA will not destroy the LED. Continuously applied higher currents, say, 50 mA or 60 mA, may lead to higher light energy output, but also to a reduced life span of minutes, or seconds. To give an example of a possible limitation, we tried to find out where a maximum may be reached for a specific LED type. In so-called ultra bright red LEDs, the life span was less than five minutes when 60 mA were continuously applied. However, pulsed loading of the LEDs with much higher currents is well tolerated.
German Pat. No. DE 3,432,018 to Nagasaki et al., U.S. Pat. No. 4,816,909 to Kimura et al., U.S. Pat. No. 5,363,135 to Inglese disclose the use of light emitting diodes arranged in the tip part of the insertable part of an endoscope to provide illumination for imaging, more specifically, to adjust for image sensor devicexe2x80x94specific conditions and requirements, such as adjustment for pixel numbers, spectral characteristics, and image colour separation. However, the above mentioned inventions do not teach and cannot be applied to obtain stroboscopy illumination, because no triggering parts including a frequency detecting device (e.g., for the human voice) are incorporated. Furthermore, the above mentioned inventions do not provide means for matching single pulses of light with individual frames in a camera system. Stroboscopy features prominent in the present invention are therefore not anticipated in the abovementioned patents.
Whatever the precise merits, features and advantages of the above cited references and prior art, none of them achieves or fulfills the purposes of the present invention. A principal object of the present invention is a system for stroboscopic endoscopy that is small, light weight, and inexpensive to build. The prior art devices fail to be satisfactory, because they do not utilize the advantages of pocket-sized electronics, are not power outlet independent, are not portable for hand-held examinations, are not cheap to build, and do not provide to match light pulses to the active frame intervals of image recording systems, as is all provided in the present invention. Customly available light sources for clinical rigid and flexible stroboscopy are heavy (they weigh more than 5 kg), they are all power outlet dependent, and they are mostly based on xenon or halogen light emitting bulbs with far more than one hundred Watts of energy consumption, leading to heat emission undesireable for endoscopy, and cost at least 5,000 US$. The main prerequisites for future clinical needs of small sized, light-weight, and inexpensive stroboscopy devices (Wendler, 1992) are still not met.
It is another principal object of the present invention to provide an electronic control unit within the endoscopy illumination system with characteristics that will enable achievement of sufficient illumination of the objects inside the body. Among the features necessary for stroboscopy are short light pulses with high intensities, rapid increase and more rapid decay than xenon light bulb flashes, machine-set fixed and/or externally triggered flashing capabilities from lower than 100 Hz up to more than 400 Hz. All above mentioned features are realized in the present invention.
It should be noted that use of inexpensive, detachable light-emitting elements, such as LEDs for diagnostic procedures, may have the additional potential of being used only once. Single-use light-emitting elements could reduce costs by avoiding the need for special sterilization procedures.
Another object is to provide a device that can be disassembled quickly and easily for transportation to an examination site, such as in a bedside patient examination procedure, or quick follow-up examination outside the office site, and that allows for more practical screening of a large population. The availability of an inexpensive and versatile stroboscopic endoscope could have a positive impact on the health of many people in developing countries.
To avoid double exposures, it is important that the illumination source flash only once per video frame. The electronic control unit of the present invention may be designed to ensure that only one flash accompanies a single image acquisition, thus avoiding double exposures and the resulting blurred images during stroboscopy recordings.
The abovementioned features can all be realized, when our endoscopy illumination system is used in combination with ultra bright LEDs within its light-emitting element.
The principal object of the present invention is to provide an endoscopy illumination system comprising light-emitting elements such as light emitting diodes, driven by an electronic control unit. The system should be light-weight, easily portable, pocket-sized, power outlet independent, easy to handle, and inexpensive, while also providing sufficient illumination for stroboscopy purposes. Pulsed light from said light-emitting element, powered and controlled by said electronic control unit, provides adequate light pulse emissions for direct visual examination, as well as adequate illumination, when image processing devices, including solid state cameras, CCD and CMOS, and image recording systems are attached.